Controller for electric motor driven devices



y 1937- R. G. LOCKETT 2,079,124

CONTROLLER FOR ELECTRIC MOTOR DRIVEN DEVICES Filed Sept. 8, 1956 UP DOWN@WWN 3% WWW I38 WXM Patented May 4, 1937 UNITED STATES CONTROLLER FORELECTRIC MOTOR DRIVEN DEVICES Ralph G. Lockett, Wauwatosa, Wis.,assignor to Cutler-Hammer, Inc.

, Milwaukee, Wis., a corporation of Delaware Application September 6Claims.

This invention relates to improvements in controllers for electric motordriven devices.

In practice there are instances where it is desired to drive the drivendevice in a given direction into a limit, then to effect a relativelysmall reverse movement of the driven device, and thereafter to effect arelatively small movement of the driven device in the first mentioneddirection preparatory to effecting return of the driven de- 10 vice toits initial position. Such control is desired in connection with rollerdams where for inspection a roller is hoisted to a given position andthen lowered slightly on to hooks to relieve the hoisting chains ofstrain. The hooks are 15 ordinarily manually placed in position beneaththe roller when hoisted to the given position, and the roller iscustomarily again hoisted to allow withdrawal of the hooks.

As in the example of the roller dam it is sometimes necessary to employgeared limit switches as distinguished from those subject to directactuation, whereas the reverse movement of the driven device to bring itinto the desired position of rest is so slight as to render exceedinglydifficult resetting of the limit switch relied upon to arrest theinitial operation mentioned. Thus where further operation in the initialdirection is needed preparatory to further reverse operation greatdifficulty has been experienced in affording 30 a simple, inexpensiveand reliable control.

This invention has among its objects to overcome the difiicultiesheretofore experienced in such instances, and particularly to avoid needof resetting the limit switch in order to obtain the cycle mentioned.

Another object is to provide simple, inexpensive and reliable meanswhich will afford the aforementioned cycle of operation and which mayreadily be incorporated in a controller affording 40 such additionalcontrol of the roller dam or other device as may be desired.

Various other objects and advantages of the invention will hereinafterappear.

The accompanying drawing illustrates" diagrammatically one embodiment ofthe invention, it being understood that the invention may be embodied inother forms without departing from the scope of the appended claims.

In the drawing,

Fig. 1 is a circuit diagram, while Fig. 2 is a limit switch diagram.

Referring to Fig. 1 of the drawing, the same shows an alternatingcurrent motor I which it may be assumed is employed to raise and lower arollerdam. As will be understood, it is cus- 8, 1936, Serial No. 99,799

tomary to provide for various operations of the dam roller, but forsimplicity of illustration many of the provisions of the usual controlhave been omitted from the drawing.

As illustrated the motor is supplied from lines L L and L throughreversing switches 2 and 3. The left hand terminal of the motor isconnected directly to line L while the right hand terminal of the motoris adapted to be connected to line L through the right hand pole ofswitch 2, or alternatively to line L by the right hand pole of switch 3.The center terminal of the motor is adapted to be connected to line Lthrough the left hand pole of switch 2, or alternatively to line Lthrough the left hand pole of switch 3. As will be understood, it iscustomary to provide an additional contactor for interrupting all lineconnections of the motor, but such contactor has been omitted forsimplicity of illustration. It may be assumed that closure of switch 2effects operation of the motor to raise the dam roller, while closure ofswitch 3 efiects reverse operation of the motor to lower the dam roller.

The additional control means illustrated comprises a push buttom switch4 to complete an energizing circuit for the up reversing switch 2through a limit switch 5, and a push button switch 6 to effectenergization of down reversing switch 3. The switch 6 effectsen-ergization of reversing switch 3 by energizing a relay '1 which inturn closes the energizing circuit of reversing switch 3, through alimit switch I l. The relay 1 has contacts 1 to complete the connectionsdescribed, and also has contacts l which complete an energizing circuitfor a relay 8 through limit switches 8, l0 and I2, and relay 8 hascontacts 8 to short-circuit limit switch 5, and contacts 8' to establishfor itself a maintaining circuit through limit switches ill and 12.

Referring to Fig. 2, the limit switches which in practice may be of anypreferred type are arranged to be actuated by the driven device in anypreferred manner as through a screw and traveling nut so that when thedam roller is raised to a given position limit switch will open and whenthe roller is raised to a second given position the limit switch Illwill open. The limit switch 9 which is shown open is arranged to beclosed when limit switch 5 opens, while the limit switch I I is arrangedto be opened when the dam roller is moved downward to some givenposition below its aforementioned hooked position. The limit switch l2which is shown open is arranged to be closed slightly aheadof limitswitch 9 as the dam roller is raised and to bereopened after reclosingof limit switch l and reopening of limit switch 55 when the dam rolleris lowered.

The control circuits above mentioned are supplied from lines L and Lthrough a suitable knife switch #5 and. fuses l6. Also the connection toline L includes a low voltage switch ll having an operating and holdingwinding l'l connected across lines L and L below the switch H. Toinitially energize the winding Il to close the switch ll there isprovided a push button switch !8 in accordance with the usual practice.

As will appear, use of the means controlled by push button switch 5 tolower the dam roller below its hooks effects needless operations ofcertain of the instrumentalities, and as illustrative of otherwiseproviding for lowering below the hooks there is shown a push buttonswitch I!) which directly energizes reversing switch 3 subject todeenergization by limit switch ll.

Considering now in further detail the control afforded by theinstrumentalities illustrated, and assuming the dam roller to be loweredto the limit set by limit switch ll it may be raised by pressing pushbutton 4. Closure of push button switch 4 completes circuit from line Lthrough switch l5, a fuse i6 and switch I! to and through the limitswitch 5, by conductors and 21 through the winding of reversing switch 2by conductors 22 and 23 through a fuse l6 and switch i5 to line L Thusassuming continued depression of the push button switch 4 the motor isstarted and raises the dam roller until the limit switch [2 is closedand the limit switch 5 is opened. During this roller raising operationthe relay 8 remains inefiective to close the shortcircuit around thelimit switch 5, due to the fact that the limit switch 9 in circuit withthe winding of the relay 8 is open.

After the roller has been arrested by opening of the limit switch 5which as aforestated effects closure of limit switch 9, the roller maybe lowered on to its supporting hooks by operation of push button switch6. Closure of switch 6 completes circuit from line L though the windingof relay 1 by conductors 24, 25 and 23 to line L Relay 1 then responds,completing circuit from line L through its contacts I by conductor 26through the winding of reversing switch 3, by conductors 2? and 23 toline L This effects lowering of the dam roller and when the rollerengages its supporting hooks the push button switch 6 is released todeenergize reversing switch 3 to stop the motor.

At the same time that the relay energizes the reversing switch 3 itcompletes a circuit from line L through its contacts l to and throughthe now closed limit switch 9 and limit switches 10 and 42 to andthrough the winding of relay 8 by conductors 28, 25 and 23 to line LRelay 8 thereupon responds to establish through conductors 29 and 3G ashort-circuit for limit switch 5, and furthermore to establish foritself a maintaining circuit which extends from line L by conductor 3|through contacts 8 by conductor 32 through limit switches l0 and I2 toand through its winding as already traced. Thus relay 8 is maintainedenergized to maintain the limit switch 5 short-circuited after theswitch 6 is released and relay 1 is deenergized, and as will be apparentthis short-circuit of limit switch 5 again renders push button switch 4effective when depressed to energize reversing switch 2.

Thus when it is desired to lift the dam roller from its hookspreparatory to lowering said roller it is only necessary to againdepress switch 4 to energize reversing switch 2. Assuming the pushbutton 4 to be held depressed, the roller will be raised until limitswitch I0 is opened whereupon relay 8 will be deenergized to interruptthe circuit of reversing switch 2, said relay remaining deenergizeduntil switch 6 is again operated.

After the dam roller has been raised from its hooks and arrested by theopening of the limit switch I!) the roller may be lowered by depressingpush button switch l9. This establishes a circuit paralleling thecontacts I of relay 1, thus completing the energizing circuit ofreversing switch 3 subject to interruption thereof by limit switch ii.Should the switch 6 be depressed instead of switch [9 it also wouldenergize reversing switch 3 in so doing would energize relay which inturn would again energize relay (2 opening of limit switch I2 which asexplained opens upon resetting of the limit switches used in placing thedam roller on its hooks and removing it therefrom, whereby interferencewith subsequent hooking operations is prevented.

If after response of the relay 8 to short-circuit limit switch 5 ashereinbefore set forth there should be a failure of voltage said relaywill not respond automatically upon restoration of voltage. However, therelay may be reset by momentarily closing push button switches l8 and 6to reset the low voltage relay and to energize momentarily the relay 1,the latter in turn reenergizing relay 8 which upon respondingreestablishes its maintaining circuit.

What I claim as new and desire to secure by Letters Patent is:

1. In a controller for a motor utilized to drive a device in onedirection to a given limit, then return it a slight distance to a givenposition, and thereafter drive it in the direction first mentioned to asecond limit, in combination, means for effecting operation of the motorin reverse directions selectively, a limit switch to stop the motor whenthe driven device is driven as aforestated to the first limit, and alimit switch to stop the motor when the driven device is subsequentlydriven to said second limit, said means comprising means to effect aftertripping of the first limit switch completion of the aforestated cyclewhile said first limit switch remains tripped.

2. In a controller for a motor employed to drive a device in onedirection to a first limit, then return it a relatively slight distanceto a given position, and thereafter continue its drive in the directionfirst mentioned to a second limit, in combination, means for effectingoperation of the motor in reverse directions selectively, a limit switchto stop the motor when the driven device is driven as aforestated tosaid first limit, and a limit switch to stop the motor when the drivendevice is driven to said second limit, said means comprising means toshunt the first mentioned limit switch when the motor is reversedfollowing the tripping of said first limit switch and for maintainingsaid shunt pending motor operation to trip the second mentioned limitswitch.

3. In a controller for a motor employed to drive a device in onedirection to a first limit, then return it a relatively slight distanceto a given position, and thereafter continue its drive in the directionfirst mentioned to a second limit, in combination, means for effectingoperation of the motor in reverse directions selectively, a limit switchto stop the motor when the driven device c. However, relay 8 would bedeenergized upon is driven as aforestated to said first limit, and alimit switch to stop the motor when the driven device is driven to saidsecond limit, said means comprising a relay responsive upon reversal ofthe motor after tripping of the first mentioned limit switch to shuntthe latter and to establish for itself a maintaining circuit includingthe second mentioned limit switch.

4. In a controller for a motor employed to drive a device in onedirection to a first limit, then return it a relatively slight distanceto a given position, and thereafter drive it in the direction firstmentioned to a second limit, in combination, means comprising two pushputton switches to effect reverse operation of the motor, the directionbeing determined by the push button pressed, a limit switch to stop themotor when the driven device is driven as aforestated to said firstlimit, a second limit switch to stop the motor when the driven device issubsequently driven to the aforementioned second limit, said meanscomprising means rendering said two push button switches eifective todirect the full cycle aforementioned and to render non-essential tocontinuance of the cycle resetting of the first limit switch.

5. In a controller for a motor employed to drive a device in onedirection to a first limit, then return it a relatively slight distanceto a given position, and thereafter continue its drive in the firstmentioned direction to a second limit, in combination progressivelyoperated limit switches and means for effecting motor operation inreverse directions, said means comprising means to shunt the firsttripped limit switch when reversing the motor operation and to stop themotor while maintaining said shunt, and further comprising means tointerrupt said shunt upon tripping of the second limit switch.

6. In a controller for a motor employed to drive a device in onedirection to a first limit, then return it a relatively slight distanceto a. given position, and thereafter continue its drive in the firstmentioned direction to a second limit, in combination progressivelyoperated limit switches and means for effecting motor operation inreverse directions, said means comprising means to shunt the firsttripped limit switch when reversing the motor operation, and to maintainsaid shunt subject to interruption by tripping of another of said limitswitches and further comprising a push button switch effective to startthe motor for arrest by one of said limit switches and to restart themotor for arrest by another of said limit switches.

RALPH G. LOCKETT.

